Plastics are everywhere – from cell phones to soda bottles, to trash on the beach and in our oceans. Yet while our lives are dominated by plastic, plastics and their environmental impacts are still largely misunderstood by many people. This three part series explores plastics—from their creation to what happens once they go in your trash can or recycling bin. Part I begins by answering the first big question: “What are plastics?!”
While some plastics are naturally found in the environment, the majority are man-made. Man-made plastics are created when individual carbon molecules are chemically bonded together. These carbon molecules are typically extracted from oil, a non-renewable resource, but more eco-friendly alternatives use carbon derived from natural materials like corn oil. Individual carbon molecules are combined to create compounds like styrene, ethylene and formaldehyde.
There are nearly limitless ways in which carbon molecules can be combined, which allows the creation of hundreds of types of plastics. One of the most prized characteristics of plastic is its ability to remain chemically inert when mixed with other substances.
This allows, for example, the storage of substances such as alcohol and gasoline in plastic containers, without compromising the integrity of the container itself. However, because plastic does not react chemically with other substances, it also does not easily decay. In fact, plastic never actually goes away in the environment—it just breaks down into smaller and smaller pieces.
Another important chemical property of plastic is its ability to be easily molded into a variety of shapes, a characteristic that allows it to be extremely versatile and used in numerous applications. Plastics can be divided into two major categories: thermoset plastics that retain their shape once cooled and hardened, and thermoplastics that are less rigid and can return to their original form upon heating.
Thermoset plastics are used for auto and aircraft parts, while thermoplastics are easily molded and extruded into fibers, packaging and films. Within these two broad categories are numerous types of plastics:
- Polyethylene terephthalate (PET or PETE) is the main plastic in ziplock food storage bags;
- Polystyrene (Styrofoam) is formed by styrene molecules. It can form a hard impact-resistant plastic for furniture, cabinets and utensils and when heated and air blown, forms Styrofoam;
- Polyvinyl Chloride (PVC) is a thermoplastic commonly used for pipes and plumbing because of its durability and low cost as compared to metals;
- Polyethylene is a type of plastic that comes in two forms: LDPE and HDPE
- Low-density polyethylene (LDPE) will float in a mixture of alcohol and water and is soft and flexible. It was first used to insulate electrical wires, but today it’s used in films, wraps, bottles, disposable gloves and garbage bags;
- High-density polyethylene (HDPE) is a harder plastic than LDPE and sinks in an alcohol-water mixture. Today, HDPE is used mostly for containers.
Plastics have proven revolutionary to our society, and we can thank plastics for hundreds of technological advances in science, medicine, space exploration, communication—you name it, plastics have played a crucial role. Yet despite the importance of plastic in today’s world, plastics have also proven to be one of the world’s biggest environmental issues.
Stay tuned for Part II: Where Does Plastic Go?